An animal model of acute hepatic failure which closely resembles human fulminant hepatic failure has been developed in rabbits with a view to testing the effectiveness of hemoperfusion through columns of various adsorbents as a means of providing temporary hepatic support. The model induced has the advantages of being (1) non-hazardous to personnel, (2) reproducible, (3) potentially reversible and (4) closely resembling human fulminant hepatic failure in its clinical, electroencephalographic, serum biochemical and hepatic histological features. The hypothetical effects of different hemoperfusion schedules on the kinetics of depletion of a protein-bound substance unconjugated bilirubin have been simulated using a computer. The results suggest that simple alterations in the schedule of hemoperfusions might accelerate depletion of toxins from an extravascular pool and hence promote earlier arousal and possibly more frequent survival in patients with fulminant hepatic failure. The ability of columns containing various adsorbents to extract potentially encephalopathic substances from plasma has been assessed. The overcome problems of biocompatibility of certain hemoperfusion columns a circuit has been devised in which a dialysate of blood from rabbits is passed over a column of an adsorbent.